Process for shucking a mollusk

ABSTRACT

Raw mollusks at room temperature are fed to a crusher wherein a mechanical shock is introduced to the mollusks with the magnitude of the shock being sufficient to release attachment between the mollusk meat and the mollusk shell by rapidly accelerating and then rapidly decelerating the mollusks using a rotating roller having a minimum surface speed of about 2800 feet per minute. The mollusks are then separated into a first stream of loose meat and meat attached to shells and a second stream of loose meat and shells. Each stream is then subjected to centrifugal separation whereupon the first stream shells having meat attached thereto is recycled through a crusher.

COMPANION CASE

This application is a CIP of my pending application Ser. No. 916,314filed June 16, 1978 and entitled Process For Shucking A Mollusk now U.S.Pat. No. 4,198,728.

BACKGROUND

Mollusks is a generic name of a number of so-called seafoods includingclams, oysters, scallops, etc. The process of opening and removal of themeat from the shell is known in the trade as shucking. Shucking has beenaccomplished heretofore manually and by apparatus. Shucking by apparatusis preferable for the economies involved since shucking by hand is slow,tedious and expensive.

It is known to mechanically shuck mollusks by first heat treating themollusks or freezing them and then subjecting the mollusks to shock by arotating roller and breaker bar. As set forth in U.S. Pat. Nos.2,832,989 and 3,665,554, mollusks are subjected to a mechanical shockwhich is sufficient to weaken the muscles and/or slightly open the shellwithout damaging the shell. Thereafter, the mollusks in said patents aresubjected to a heat treatment and then are subjected to a second shockwhich opens and/or separates the meat from the shell. The requirementfor pretreating the mollusks by heat or refrigeration unnecessarilycomplicates the process, adds to the cost of the process, and/or makesit impractical to use the process at sea where it is desired toimmediately shuck mollusks abroad ship.

Thus, prior processes heretofore which utilize mechanical shock do so inconnection with other processing steps involving heat or refrigerationas a means for weakening the muscle and the attachment of the meat tothe shell.

The texture of meat shucked without heat is quite different from thatshucked with heat. Meat shucked without the application of heat is moretender. Excessive toughness is a problem in some forms of mollusk meatproducts. Thus, tenderization achieved by this process in these productsis a significant advantage.

I have found that the yield when practicing the method of my abovementioned application can be increased by recycling one of the streamsafter centrifugal separation of both streams.

SUMMARY OF THE INVENTION

The present invention is directed to a process for shucking mollusks andincludes feeding raw mollusks at room temperature with or without anyprior heat treatment to a crusher. A mechanical shock is introduced tothe mollusks in the crusher with the magnitude of the shock action beingsufficient to release the attachment between the mollusk meat and themollusk shell without breaking up the meat to any substantial extent.The meat and shells are separated into first and second streams whereinthe first stream has loose meat and meat attached to a shell. The secondstream is shells and some inadvertant loose meat. Each stream issubjected to a centrifugal separator or equivalent so as to separate theloose meat in each stream. The meat attached to shells from the firststream is then subjected to a repeat of the crushing step.

The measure of efficiency of any shucking process is the yield measuredin pounds of meat per bushel or mollusk. The present process has yieldswhich are compatible with efficient processes used commerciallyheretofore and better than some of the lesser efficient processes usedheretofore while at the same time materially reducing both capitalinvestment and operating costs. Energy consumed by the present processis a small fraction of that consumed by most commercial processes usedheretofore. Production capacity is increased not only at greater reducedinvestment but also because the present invention uses a fraction of thephysical space required by the process used heretofore. As a resultthereof, the present invention lends itself to processing mollusksaboard ship whereby there will be less loss due to softness,deterioration due to time and temperature and breakage because of thefirmer, tougher texture of the live, cold, freshly caught mollusks.Since shucked mollusks take less room than unshucked mollusks, a shipcan bring in a larger payload.

It is an object of the present invention to provide a method forprocessing mollusks in a manner which is simple, inexpensive, andefficient.

It is another object of the present invention to provide a process forshucking a mollusk which can be performed onboard ship using live,freshly caught mollusks whereby the shells may be thrown overboardthereby eliminating a disposal problem, the meat is firmer, and the shipcan bring in a larger payload.

Other objects will appear hereinafter.

For the purpose of illustrating the invention, there is shown in thedrawings a form which is presently preferred; it being understood,however, that this invention is not limited to the precise arrangementsand instrumentalities shown.

FIG. 1 is a perspective view of apparatus which can be utilized inpracticing the present invention.

FIGS. 2-4 are sequential illustrations of a mollusk such as a clam beingprocessed with the views being taken along line 2--2 in FIG. 1.

FIG. 5 is a graph of acceleration in time versus rpm.

FIG. 6 is a recycling diagram.

Referring to the drawings in detail, wherein like numerals indicatedlike elements, there is shown the preferred apparatus when practicingthe present invention.

The apparatus designated generally as 10 includes three major componentsnamely the crusher 12, the washer 14, and the separator 16. The crusher12 includes a housing designated generally as 18. The housing 18includes wall 22 which interconnects the parallel walls 20 and 24.Opposite wall 22, there is provided a plate 26 hinged for pivotablemovement at its upper edge by hinge pins 30 connected to the side walls20, 24. Plate 26 is provided with a weight 28 attached thereto or isspring biased to the position shown in FIG. 2.

A roller 32 is rotatably supported by bearings on the walls 20, 24.Roller 32 may have a substantial diameter such as 14 to 18 inches. On an18 inch diameter roller 32, there is provided a plurality of staggeredrows of projections 34 which project outwardly for a distance of about 2inches. The roller 32 and its projections are made of steel or someother hard metal. Roller 32 may be solid or hollow. Roller 32 is drivenby motor 36 which is preferably a variable speed motor having asufficiently high operating range whereby it may rotate the roller 32 atspeeds up to about 1000 rpm.

The bottom wall of the housing 18 slopes downwardly into a downwardlyangled chute 38. Chute 38 tapers inwardly and discharges into a drum 40that is open at each end. Drum 40 is provided with tires on its outerperiphery each rotatably supported by a roller 42 so as to rotate aboutan axis which is slightly inclined so that the discharge end thereof isslightly below the inlet end at the chute 38.

A motor 44 has a gear 46 connected to its output shaft. Gear 46 isconnected to a gear 48 surrounding the drum 40. The drum 40 is rotatedabout is longitudinal axis by motor 44. The inner periphery of drum 40is provided with a plurality of helically arranged ribs 50. A conduit 52has its discharge end adjacent the inlet end of drum 40 for introductionof water into the drum 40.

The discharge end of drum 40 is disposed above a trough 54. Trough 54 isshallow and has a weir 55 adjacent one end containing the outlet 56. Anendless conveyor having cleats thereon and designated 58 is supported bythe shallow trough 50. Conveyor 58 is driven by motor 60. Motor 60 issupported by a bracket on the trough 54. If desired, a container 62 maybe provided adjacent the discharge location of conveyor 58.

The housing 12 is preferably provided with a hopper having a walloverlying that portion of the upper end of walls 20, 24 adjacent theplate 26. Mollusks such as clams are fed by conveyor or by gravitythrough a hopper to the upper end of the crusher 12. The roller 32 ispreferably rotating with a minimum surface speed of about 2800 feet persecond. On an 18 inch diameter roller 32, motor 36 rotates the rollerwith a preferred minimum speed of 600 rpm. The projections 34 contactthe clams and rapidly accelerate the same by pushing along a side edgeof the clam. The clam is then rapidly decelerating by contact with thebreaker bar 27 during which the shell is broken. The forces imparted tothe breaker bar 27 cause the plate 26 to pivot from the position shownin FIG. 2 to the position shown in FIG. 4 whereby the meat and brokenshell fall into the chute 38.

By gravity, the meat and broken shell are introduced into the drum 40having perforations of about 1/8 inch. While passing through the drum40, the meat is washed and any sand associated therewith is separatedfrom the meat by draining with the washwater through the holes in theside of the drum to a collection trough not shown. Drum 40 may dischargethe meat and shells to separator trough 54 filled with brine having ahight salt concentration. The shells have a higher specific gravity andtherefore fall to the bottom of the trough 54 and are removed therefromby the conveyor 58. Conveyor 58 may discharge the shells overboard whenthe apparatus 10 is on a ship. If more convenient, conveyor 58 maydischarge the shells into a container 62. The meat has a much lowerspecific gravity and therefore will float with the brine over the weir55 and through the outlet 56 to mesh separating screen. The separatingscreen has perforations sufficiently small so as to retain the meatwhile permitting the brine to discharge into a suitable receptacle andfrom which the brine may be pumped to manifold 57 in trough 54 forreuse.

While passing through the crusher 12, the clam was subjected to amechanical shock action of suficient magnitude so as to release theattachment between the meat and the shell without breaking up the meatto any substantial extent. Thus, it would be undesirable to pulverizethe meat. The consuming public prefers to have large chunks of clam meatas opposed to very fine pieces of clam meat. The shock action is acombination of shearing and crushing forces applied by the projections34 and the breaker bar 27 with simultaneous rapid deceleration of theclam. Rapid acceleration just prior to the crushing and shearing adds tothe effect.

In FIG. 5, there is illustrated a graph of acceleration and time versusspeed. On the basis of testing the present invention, I have found thatwhen the surface speed is substantially below about 2800 feet per minute(an 18 inch diameter roller driven at 600 rpm), there are fair to poorresults on efficiency in that the meat tends to remain attached to theshell portions whereby the yield is low or unacceptable. Beginning atabout a surface speed of 2800 feet per minute, and at speeds thereabove,there is a good release between the meat and the shell so as to resultin a satisfactory yield. The speed may be as low as 400 rpm (surfacespeed of about 1900 fpm) if one is willing to accept only a fair yield.Since it is inefficient to rotate the roller at speeds in excess of thatneeded for a good yield, the roller 32 need not be rotated above speedsof about 1000 rpm. As will be apparent from FIG. 5, the presentinvention subjects the clams to acceleration forces of between about3000 and 8000 feet per second.

The present process eliminates the need for preheating the mollusks. Ihave found that no heat is much more efficient in yield than largeamounts of heat which are inadequate to relese the meat from the shell.I have found that the most efficient yields with the present inventionare attained when the projection 34 pushes the shell with a line offorce along a side edge of the mollusks parallel to the shell-muscleattachment surface. The weight 28 may be variable so as to accommodateto different sized mollusks with heavier weights being utilized with thelarger sized mollusks. The weight 28 should bias the plate 26 to agenerally vertical disposition whereby the projections 34 will justclear the breaker bar 27 in the absence of a mollusk and will cause theplate 26 to be pushed away from the surface of the roller 32 when theshell is being broken to facilitate discharge of the shell and meat intothe chute 38. Suitable limit stops are provided to prevent the plate 26from swinging sufficintly close to the roller 32 whereby the projections34 contact the breaker bar 27. If the mollusk is fairly clean, washerdrum 40 may be eliminated whereby chute 38 would discharge directly intotrough 54.

The preferred handling of the mollusks after initial separation isillustrated in FIG. 6. Outlet 56 is the inlet to conduit 68 which isconnected to a centrifugal pan washer 70 or equivalent and constitutes afirst stream of loose meat and meat attached to a piece of shellscreened at outlet 56 to a size less than one inch. At the washer 70,the loose meat is separated from the meat attached to a piece of shell.The latter is directed to an auxillary crusher 72 where the aboveprocess is repeated. Crusher 72 is the same as but smaller than crusher12. Thereafter the crusher 72 directs the stream to separator 74. Meatis directed from separator 74 to conduit 68 while the shells aredirected to conduit 76.

Conduit 76 corresponds to container 62 and receives the shells and someloose meat from separate 16. Conduit 76 defines the second stream andcommunicates with a centrifugal pan washer 78 or equivalent. At washer78 the second stream is divided into shells and loose meat.

Meat attained by the process of my above mentioned application is muchsofter in texture as compared with conventional processes. If it isdesired to use meat attained by my process with meat attained by aconventional shucking process, it was necessary to slightly modify theprocess. Meat which had identical texture/firmness in soup to that ofconventionally processed clams was attained as follows. The clams wereblanched for 1 minute at 170° F. and then shucked as described abovewith the speed of roller 32 being at 400-500 rpm. Thereafter the meatwas blanched at 210° F. for 10-20 seconds to deactivate enzymes forstability of storage. The first blanching step does not assist inrelease of the meat.

If 30,000 lbs of raw clams are processed, the first stream will be about3000 lbs of meat and 6000 lbs of shells with about 450 lbs of meatattached. The second stream will be about 12,000 lbs of shells and about400 lbs of loose meat. Another 6000 lbs of shells are added to thesecond stream from crusher 72. About 3400 lbs of meat is obtained fromwasher 70 and about 400 lbs of meat washer 78. The remainder of theweight is sand, water, etc. Thus, recycling in this manner increases theyield from about 3000 lbs up to about 3800 lbs.

The present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof and,accordingly, reference should be made to the appended claims, ratherthan to the foregoing specification, as indicating the scope of theinvention.

I claim:
 1. A process for shucking mollusks comprising:(a) feeding rawmollusks to a crusher, (b) introducing a mechanical shock action to themollusks in said crusher with the magnitude of the shock action beingsufficient to release the attachment between the mollusk meat and themollusk shell, (c) performing step (b) in a manner so that the mollusksare rapidly accelerated and then rapidly decelerated and are subjectedto a combination of shearing and crushing forces applied by twocooperating elements which break the shell while the mollusks aredecelerated, (d) dividing the shucked mollusks into a first stream ofloose meat and meat attached to a piece of shell and a second stream ofshells and inadvertant loose meat, (e) separating out the loose meat ofthe first stream, (f) recycling the remainder of the first stream as persteps (b) and (c), separating any meat from the shells after the secondshock action and adding the separated meat to the meat attained in step(e), (g) separating the loose meat of the second stream from the shellsand adding such loose meat to the meat of step (e).
 2. A process inaccordance with claim 1 including using a centrifugal pan washer duringthe separating steps (e) and (g).
 3. A process in accordance with claim1 including using a roller as one of said cooperating elements with aspeed of 400-500 rpm, and blanching said mollusks at a temperature andfor a length of time which is insufficient to cause release of meat fromits shell to thereby increase the firmness of the meat texture forblending with other meat having firm texture.
 4. A process in accordancewith claim 1 wherein said steps are performed on board a sea goingvessel with freshly caught mollusks without any heat treatment of themollusks sufficient to release meat from the shells.